The present invention relates to a storage unit for use as an external storage unit for a computer. More particularly this invention relates to a storage unit capable of improving the data transmission efficiency and reducing the seek time.
As an external storage unit for computer, a storage unit employing a circular magnetic disk unit as a storage medium has been used. Upon read/write (R/W) operation in this storage unit, a seek operation for moving a read/write head to a desired track on the recording medium is necessary. Because it takes time for command processing until the read/write head actually moves since a seek command for instructing this seek operation is issued, a seamless seek operation can not be achieved. Further, because an inductance component is contained in a unit for driving the read/write head, there exists a voltage transition period. Thus, a delay time occurs until the read/write head actually moves since a voltage is supplied to this storage unit, and this delay time further prolongs the seek time. The above-mentioned decline in the data transmission efficiency and prolongation of the seek operation are important problems which obstruct increased density trend of the storage unit and therefore, a method for solving such a problem has been demanded.
FIG. 33 is a block diagram showing a structure of a conventional storage unit 2. The storage unit 2 is connected to a host 1 such as computer through a small computer system interface (SCSI) bus and executes read/write to a recording medium (magnetic disk) (not shown) based on a read/write request command S01 from this host 1. Here, the aforementioned read/write request command S01 contains target cylinder information for instructing a cylinder in the recording medium, target sector information for instructing a sector in the recording medium and head information for instructing a read/write head 13 using at the time of the read/write operation. A sector specified by the target cylinder information and the sector information is a region to be subjected to read/write.
In this storage unit 2, a command/status processing section 3, a position information conversion section 4, a seek command issuing section 5 and a read/write control section 6 compose a upper level controller 7. In this upper level controller 7, the command/status processing section 3 carries out such processing as reception of a read/write request command S01 from the host 1 and report of status of the storage unit 2 to the host 1. The command/status processing section 3 outputs the target cylinder information, target sector information and target head information contained in the received read/write request command S01 to the position information conversion section 4 as local block address (LBA) S02.
The position information conversion section 4 outputs the target cylinder information and head information of the target cylinder information, target sector information and head information obtained from the above LBA S02, as the position information S03 to the seek command issuing section 5 and outputs the target sector information to the read/write control section 6 as the read/write object sector data S07. Here, the read/write control section 6 controls the read/write operation. The seek command issuing section 5 is triggered when a read/write completion report S06 which indicates that a last read/write operation is completed is inputted from the read/write control section 6 so as to issue a seek command S04 for carrying out the seek operation and this seek command is outputted to a detailed target position setting section 8.
A head positioning control section 10 controls positioning of a read/write head 13 described later on a recording medium (not shown) and comprises the detailed target position setting section 8 and a seek command executing section 9. The position of the read/write head 13 differs during reading and writing due to the influence of yaw angle. The detailed target position setting section 8 outputs target position to the seek command executing section 9 as the detailed target position information S10 considering a correction corresponding to the difference in this yaw angle.
The detailed target position setting section 8 receives a feedback of the present position S23 of the read/write head 13 which will be described later and then outputs a detailed target position information S10. The seek command executing section 9 outputs a voice coil motor (VCM) voltage S11 based on the detailed target position information S10. A power amplifier 11 amplifies the aforementioned VCM voltage S11 and supplies a VCM current S12 which is a driving current to the VCM 12.
A disk enclosure (DE) 16 includes the voice coil motor (VCM) 12, the read/write head 13, a preamplifier 14 and a position demodulator 15 in a sealed condition. The aforementioned VCM 12 moves the read/write head 13 in a radius direction between sectors during the seek operation and this motor is driven by the VCM current S12 supplied from the power amplifier 11. Here, the amount of movement of the read/write head 13 is controlled by changing the VCM current S12. The read/write head 13 writes read/write data S19 (write data here) supplied from the read/write control section 6 on a recording medium using a magnetic field generated by a recording current amplified by a preamplifier 14. The read/write head 13 reads out data recorded in the recording medium magnetically as a playback voltage and outputs it as the read/write data S19 (read data here) to the read/write control section 6 through the preamplifier 14.
The read/write head 13 detects a servo pattern for positioning recorded in the recording medium and the preamplifier 14 outputs this detection result to the position demodulator 15 as a servo signal S13. The position demodulator 15 demodulates the present position S23 of the read/write head 13 from the aforementioned servo signal S13 and outputs it to the detailed target position setting section 8. Further, the position demodulator 15 obtains a number of a sector which the read/write head 13 currently tracks from the aforementioned demodulation result and outputs it to the read/write control section 6 as the present position sector number S09. Here, the read/write control section 6 determines whether or not the read/write operation is complete from the present position sector number S09 and read/write data S19. If the read/write operation is complete, the read/write control section 6 outputs the read/write completion report S06 to the command/status processing section 3 as well as to the seek command issuing section 5. Then, the detailed target position setting section 8 determines whether or not the seek operation is complete based on the present position S23. If the seek operation is complete, the detailed target position setting section 8 outputs the seek completion report S08 to the read/write control section 6.
Next, with reference to FIG. 34, mainly the read/write operation and seek operation in the conventional storage unit 2 will be described. In the processing and operation of the storage unit 2, as shown in the upper half of FIG. 34, command processing (1), seek operation, read/write operation and command processing (2), by which a single set is composed, are repeated in time series manner.
Here, the command processing (1) comprises a processing on the read/write request command S01 in the command/status processing section 3, target position information conversion processing in the position information conversion section 4 and an issuing processing of the seek command S04 in the seek command issuing section 5. Further, the seek operation is an operation for moving the read/write head 13 by the seek command executing section 9, power amplifier 11 and VCM 12. The read/write operation is a read/write operation of the read/write head 13 with respect to the recording medium by a control of the read/write control section 6. The command processing (2) is a processing for outputting the read/write completion report S06 from the read/write control section 6 to the command/status processing section 3 as well as to the read/write control section 6.
If the read/write request command S01 is inputted from the host 1 to the command/status processing section 3 at time t1 shown in the upper half of FIG. 34, the command/status processing section 3 generates LBA S02 from this read/write request command S01 and outputs this to the position information conversion section 4. Consequently, the position information conversion section 4 outputs the position information S03 to the seek command issuing section 5 and then outputs the read/write object sector data S07 to the read/write control section 6. If the position information S03 is inputted after the input of the read/write completion report S06, the seek command issuing section 5 outputs the seek command S04 to the detailed target position setting section 8 at time t2. With this, the command processing (1) ends.
When the seek command S04 is inputted to the detailed target position setting section 8 at time t2, the seek operation is started. When the detailed target position information S10 is outputted to the seek command executing section 9 from the detailed target position setting section 8, the VCM voltage S11 is outputted to the power amplifier 11 from the seek command executing section 9. Consequently, the VCM current S12 is supplied to the VCM 12 so as to drive it, so that the read/write head 13 begins to move on a recording medium.
When the read/write head 13 moves up to a desired position after receiving a feedback of the present position S23 from the position demodulator 15 at time t3, the detailed target position setting section 8 outputs the seek completion report S08 to the read/write control section 6. Consequently, at time t3, the read/write control section 6 waits until the read/write head 13 is placed at a desired sector obtained from the read/write object sector data S07, based on a present position sector number S09 indicating a sector number in which the read/write head 13 is currently located. If the read/write head 13 is located at a desired sector, read/write data S19 is supplied to the read/write head 13 from the read/write control section 6 through the preamplifier 14, thereby achieving the read/write operation. Then, if the aforementioned read/write operation is terminated at time t4, the read/write control section 6 outputs the read/write completion report S06 to the command/status processing section 3 as well as to the seek command issuing section 5. With this, the read/write operation corresponding to a single set ends.
When the aforementioned read/write completion report S06 is inputted to the command/status processing section 3 as well as to the seek command issuing section 5 at time t5, the aforementioned command processing (1) is carried out by the command/status processing section 3, position information conversion section 4 and seek command issuing section 5. After that, the seek operation is carried out at time t6 and the read/write operation is carried out at time t7. Finally, the command processing (2) is carried out at time t8.
As described with reference to FIG. 34, in the command processing (2), the read/write completion report S06 from the read/write control section 6 is received by the command/status processing section 3 as well as by the seek command issuing section 5 at time t5 and after the seek command S04 is issued from the seek command issuing section 5 for a next command processing (1), the seek operation is carried out at time t6. However, as evident from this figure, in the conventional storage unit 2, it takes time T1 (time t4-time t6) for carrying out the command processing (2) and command processing (1) until a next seek operation is carried out after a last read/write operation is terminated. Thus, the conventional storage unit has such a problem that data transmission efficiency declines by an amount corresponding to this time T1.
Further, in the conventional storage unit 2, because a coil is used for the VCM 12 for moving the read/write head 13, if the VCM current S12 is inputted from the power amplifier 11, it takes time until a steady condition is achieved because of inductance component of this coil. In other words, even if the VCM voltage S11 is supplied to the power amplifier 11 from the seek command executing section 9 at time t6 shown in FIG. 34, until the VCM current S12 becomes a steady current, the read/write head 13 does not move. Therefore, the conventional storage unit 2 has such a problem that a seek time required for the seek operation of the read/write head 13 is prolonged because of an influence of inductance component of the VCM 12.
Accordingly, the present invention has been made in views of the above problems and therefore it is an object of the invention to provide a storage unit capable of improving the data transmission efficiency besides reducing the seek time.
According to the first aspect of the present invention, when the seek operation is to be carried out, the control unit carries out a processing necessary for the seek operation before the read/write operation ends. That is, the processing necessary for the seek operation is carried out in parallel to the read/write operation and therefore, a time required for the above processing is saved.
According to the second aspect of the present invention, when the seek operation is to be carried out, the timing means obtains a timing for terminating the processing when the read/write operation is terminated. Then, the driving unit drives the seek unit at the above timing. Therefore, in this case, the seek operation is carried out at the same time when the read/write operation ends.
According to the third aspect of the present invention, the initial value is counted down according to the sector pulse that is inputted each time when the head passes a sector on the recording medium. Further, when this count value becomes zero, the seek unit is driven by the driving unit which is also the time when the read/write operation ends, and in this way the seek operation is carried out.
According to the fourth aspect of the present invention, the seek unit is driven by the driving unit at a timing at which the sector position in which the read/write operation is terminated matches with a sector position in which the head is positioned which is also the time at which the read/write operation is terminated, and in this way the seek operation is carried out.
According to the fifth aspect of the present invention, the initial value is counted down according to the byte pulse that is inputted each time when the head passes a byte on the recording medium. Further, when this count value becomes zero, the seek unit is driven by the driving unit which is also the time when the read/write operation ends, and in this way the seek operation is carried out.
According to the sixth aspect of the present invention, the seek unit is driven by the driving unit at a timing at which the byte position in which the read/write operation terminates matches with the byte position in which the head is positioned which is also the time when the read/write operation is terminated, and in this way the seek operation is carried out.
According to the seventh aspect of the present invention, the seek unit is driven by the driving unit at a timing in which the counting result of the timer matches with the time at which the read/write operation is terminated which is also the time when the read/write operation is terminated, and in this way the seek operation is carried out.
According to the eighth aspect of the present invention, the seek unit is driven by the driving unit at a timing at which the time required for the read/write operation matches with the counting result of the timer which is also the time when the read/write operation is terminated, and in this way the seek operation is carried out.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.